SAT contact info

[Frank Labuschagne]

Hi,
I'm looking for a reasonable solution to the rather annoying problem of finding face pairs (regardless of contact type) with discrete SAT collision detection. I've never come across a SAT implementation that actually returns reasonable contact info and having struggled with it for a while I'm starting to doubt something practical with SAT is even possible. Any insights or help would be greatly appreciated.

[projectileman]

Hi.
Actually Bullet has an alternative collision library which is based on SAT, and also gives detailed contact features (Vertex-Face-Edge). Just take a look to the Extras folder in the Bullet source:

http://code.google.com/p/bullet/source/ ... xCollision

May you might want to look into the Tokamak source, it has a nice implementation of the SAT algorithm.

http://www.tokamakphysics.com/

Also I recommend to take a look to the Oliver Renault (Olii)'s blog. He offers a very good explanation about how SAT works. Please visit
http://uk.geocities.com/olivier_rebellion/, and also download his source code: http://uk.geocities.com/olivier_rebellion/Cube3D.zip

[Erwin Coumans]

Indeed, Bullet provides an implementation of SAT with contact clipping. It hasn't been fully integrated, so it might require a bit of work.

Also check out the IBDS library, it adds a working 3D implementation of contact clipping to generate all contact points. This can be used as a contact post processing step, after you find the closest axis (for example using the SAT or GJK).

Hope this helps,
Erwin